the measurement of this fundamental parameter, Starna® offers you
the choice of either sealed cell, or filter materials. Please note
that your selection process should not only include the wavelength(s)
required, but also the spectral bandwidth (SBW) of your spectrophotometer.
Use of the reference materials outside the SBW range detailed is not
excluded, but variations from the certified values may be observe
UV Absorbance and Linearity
Description: Potassium dichromate from NIST (SRM 935a) in 0.001M perchloric
Usage: Testing absorbance scale and linearity in the UV region.
Useable range: 235 nm to 350
nm, instruments with a SBW of 2 nm or less.
Physical Configuration: UV quartz cells that have been permanently
Dichromate – UV Absorbance and Linearity
use of potassium dichromate solvated in dilute perchloric acid is
an established and well recognised method for the validation of the
absorbance scale and linearity of a spectrophotometer in the UV region.
prepared in 0.001M perchloric acid, potassium dichromate gives a spectral
scan containing characteristic peaks at 257 nm and 350 nm, and troughs
at 235 nm and 313 nm. Within the concentration range 20-100 mg/l,
if the absorbance scale of a narrow SBW (< 2 nm) spectrophotometer
is linear, the apparent absorbances of a series of concentrations
will be a linear function of concentration.
of one blank (0.001M perchloric acid) and five increasing concentrations,
with nominal values of 20 mg/l, 40 mg/l, 60 mg/l, 80 mg/l, and 100
Typical values obtained:
Starna® potassium dichromate cells are prepared using the solid NIST
primary material (SRM 935a), prepared at the solution concentrations
described in NIST Special Publication 260-54. After filling under
controlled conditions, the cells are then permanently sealed by heat
fusion and the values certified by the procedure described below.
•All Starna® potassium dichromate cells are prepared using the
solid NIST primary material (SRM 935a), prepared at the solution concentrations
described in and Use of Acidic Potassium Dichromate Solutions as an
Ultraviolet Absorbance Standard – SRM 935” (NIST Special Publication
• Primary instrumental linearity is established using the Double Aperture
•Additional traceability links to NIST primary materials are established
using SRM 930e and SRM 1930 neutral density glass filters.
•All appropriate fundamental parameters and procedures relating to
measurement, handling and storage are fully documented on the certificate
supplied with each Certified Reference Material (see